The International Maternal Pediatric Adolescent AIDS Clinical Trials (IMPAACT) Network is a new research collaboration representing a merger of investigators from the Pediatric AIDS Clinical Trials Group (PACTG) and the Perinatal Scientific Working Group of the HIV Prevention Trials Network (HPTN). The mission of the IMPAACT Network will be to significantly decrease the mortality and morbidity associated with HIV disease in pregnant women, children, and adolescents. We propose to establish a Philadelphia IMPAACT Clinical Trials Unit (PICTU) that will affiliate, by prior leadership agreement, as a priority site within the IMPAACT Network. This CTU will be comprised of an Administrative Component, two pediatric clinical research sites at the Children's Hospital of Philadelphia and St. Christopher's Hospital for Children, and a maternal/perinatal site at the Drexel University College of Medicine/Hahnemann University Hospital. The PICTU will respond to all four priority research areas identified by the IMPAACT leadership including: 1) Vaccine Research and Development, 2) Translational Research and Drug Development, 3) Optimization of Clinical Management including Co-Morbidity, and, 4) Prevention of Mother-to-Child Transmission of HIV. The PICTU will serve as a domestic unit within the Network. The PICTU is positioned to meet the enrollment requirements for the IMPAACT network. In 2004, there were 453 HIV-infected children and youth between 0 and 24 years of age, nearly all of whom are served by our pediatric sites. The Philadelphia HIV community is well-organized and highly-motivated to support the transition to new HIV/AIDS trial networks in the region and PICTU investigators have established ties with local community organizations and action groups. The PI, participating investigators, and senior professional staff have broad experience and success in the enrollment and retention of pregnant women, infants, children, and adolescents in HIV clinical trials, as well as a strong past record of leadership and scientific contributions in NIH-sponsored HIWAIDS research and within the PACTG and other HIV/AIDS research networks (REACH, ATN, HPTN). The proposed clinical research sites and their personnel have collaborated successfully as a PACTG unit in the past and have demonstrated a consistently excellent record of regulatory compliance, timely data submission, data management, and enrollment. The participating clinical research sites have demonstrated expertise in design of randomized controlled clinical treatment trials, pharmacokinetic, immunologic, virologic, and pharmacologic studies and are well-qualified to conduct IMPAACT protocols and contribute to the Network's scientific agenda. ADMINISTRATIVE COMPONENT: